1. Field of the Invention
The present invention relates to apparatus for use in oil and gas wells or the like, and particularly to packing devices commonly referred to as bridge plugs.
2. Description of the Prior Art
During the various testing or treating operations which are normally performed on an oil or gas well, there is often need to provide a means for blocking fluid flow through the well bore. One class of such devices is referred to as bridge plugs. These devices commonly include an annular sealing element for sealing against a well bore, and means for preventing flow through the bridge plug.
Such bridge plugs are often run in conjunction with conventional packers to isolate a zone in a well for testing or treating. Also, such bridge plugs may be used alone to isolate zones for service work or testing.
Usually, bridge plugs are lowered into place within the well bore on a tubing string, and are constructed to be set at their desired location within the well bore by various manipulations of this tubing string. Most often, the bridge plugs are designed to be set by setting down the weight of the tubing string on the bridge plug after a set of slips have been initially set by rotational motion of the tubing string or other means.
With these most commonly used types of bridge plugs, it is often difficult to set the bridge plug in either shallow or deviated bore holes. This is because it is difficult in such holes to set sufficient weight down on the bridge plug to create an effective seal of the sealing element of the bridge plug against the well bore. In shallow holes, the relatively short length of the tubing string simply does not weigh enough to provide sufficient weight for properly setting the bridge plug. In deviated holes, the drag of the tubing string against the bore hole subtracts substantially from the weight which can be set down on the bridge plug, causing similar problems in providing sufficient downward weight on the bridge plug to effectively seal the bridge plug against the well bore.
It has been proposed in the prior art to utilize bridge plugs which are actuated by hydraulic pressure rather than by manipulation of the tubing string. An example of such a hydraulically actuated bridge plug is shown in U.S. Pat. No. 2,946,388 to Evans.
The present invention provides a very much improved device of the type generally shown in the Evans patent.